Biodegradable polymers derived from aminoacids

Poly(amide‐ester)s derived from five α‐amino acid mixtures including glycine, DL‐and L‐alanines, DL‐ and L‐phenylalanines, and three different diols including 1,6‐hexanediol, 1,4‐butanediol and trans ‐1,4‐cyclohexanedimethanol were synthesized by interfacial, solution and melt polymerizations. All of the polymers had Tg's ranging from −6 to 50°C. The incorporation of rigid trans ‐1,4‐cyclohexanedimethanol in the main chain significantly increased the Tg of these polymers. The degree of crystallinity depended on the type of amino acid and decreased with the size of substituent on the α‐carbon in the amino acid. Biodegradation of these polymers were tested semi‐quantitatively by turbidity measurements. Enzymes used included subtilisin, pronase E, α‐chymotrypsin, fusarium , and lipase. The incorporation of trans ‐1,4‐cyclohexanedimethanol unit slowed down degradation rate. Polymers containing L‐amino acid generally degraded faster than the polymers containing DL‐amino acids. Quantitative biodegradation testings using ninhydrin analysis, total organic analysis, and weight loss done on alanine derived polymers indicated that the degradation of the polymers by pronase E occurred at the ester bonds first and was specific against L‐amino acid. The degradation was followed by slower amide bond degradation.